1. Field of the Invention
The present invention relates to a method of manufacturing a wiring substrate and, more particularly, a method of manufacturing a wiring substrate that is applicable to a thin mounting substrate on which an electronic component is mounted.
2. Description of the Related Art
In the prior art, as a method of manufacturing a wiring substrate, there is the method of obtaining the thin wiring substrate by stacking the carrier-lined copper foil, which is constructed by temporarily adhering the copper foil peelably onto the carrier copper foil, on the substrate, forming the build-up wiring thereon, and peeling the copper foil from the carrier copper foil to separate them at the boundary.
In Patent Literature 1 (Patent Application Publication (KOKAI) 2003-168868), there is set forth the method of forming the laminated body by laminating the carrier-lined copper foil, which is formed by stacking the carrier on the copper foil, on the inner layer circuit substrate, then forming through holes in the laminated body, then applying the plating to electrically connect front and back sides, and then removing the carrier together with the plated film on the carrier.
Also, in Patent Literature 2 (Patent Application Publication (KOKAI) 2001-135911), there is set forth the method of forming through holes in the copper-clad laminate, which is laminated/formed by using at least the copper foil whose double sides are processed as the outer layer, quickly by the carbon dioxide gas laser with good productivity.
In the method of manufacturing the wiring substrate in the prior art, as shown in FIGS. 1A and 1B, a carrier-lined copper foil 400 constructed by lining a copper foil 300 with a carrier copper foil 200 is laminated on a substrate 100, and then reference holes 500 passing through the carrier-lined copper foil 400 and the substrate 100 are formed in the peripheral portion by the drilling, or the like. The reference holes 500 are provided at four corners on the outside of a product area before a build-up wiring is formed, and are used for alignment or conveyance at the time of forming the build-up wiring.
In this case, since the peeling boundary of the carrier-lined copper foil 400 exposed from the side surface of the reference hole 500 has incurred mechanical damage, the peeling is often caused partially on the peeling boundary, or the peeling boundary is often brought into the easy-peel condition. Therefore, there is a possibility that, because chemicals used in the subsequent wet process to form the build-up wiring sink into the boundary, the peeling of the carrier-lined copper foil 400 spreads. And it acts as the factor to bring about a reduction in production yield. Also, since the carrier-lined copper foil is cut in a predetermined dimension to fit in with the supporting body, such a situation is supposed that the outer peripheral portion of the carrier-lined copper foil 400 is also brought into the easy-peel condition. Thus, in some cases, the similar measures must be taken.